Coke is a solid carbon fuel and carbon source used to melt and reduce iron ore in the production of steel. In one process, known as the “Thompson Coking Process,” coke is produced by batch feeding pulverized coal to an oven that is sealed and heated to very high temperatures for twenty-four to forty-eight hours under closely-controlled atmospheric conditions. Coking ovens have been used for many years to convert coal into metallurgical coke. During the coking process, finely crushed coal is heated under controlled temperature conditions to devolatilize the coal and form a fused mass of coke having a predetermined porosity and strength. Because the production of coke is a batch process, multiple coke ovens are operated simultaneously.
Coal particles or a blend of coal particles are charged into hot ovens, and the coal is heated in the ovens in order to remove volatile matter (VM) from the resulting coke. Horizontal heat recovery (HHR) ovens operate under negative pressure and are typically constructed of refractory bricks and other materials, creating a substantially airtight environment. The negative pressure ovens draw in air from outside the oven to oxidize the coal's VM and to release the heat of combustion within the oven.
In some arrangements, air is introduced to the oven through damper ports or apertures in the oven sidewall or door. In the crown region above the coal-bed, the air combusts with the VM gases evolving from the pyrolysis of the coal. However, with reference to FIGS. 1-3, the buoyancy effect, acting on the cold air entering the oven chamber, can lead to coal burnout and loss in yield productivity. Specifically, as shown in FIG. 1, the cold, dense air entering the oven falls towards the hot coal surface. Before the air can warm, rise, combust with volatile matter, and/or disperse and mix in the oven, it comes into contact with the surface of the coal bed and combusts, creating “hot spots,” as indicated in FIG. 2. With reference to FIG. 3, these hot spots create a burn loss on the coal surface, as evidenced by the depressions formed in the coal bed surface. Accordingly, there exists a need to improve combustion efficiency in coke ovens.
In many coking operations, the draft of the ovens is at least partially controlled through the opening and closing of uptake dampers. However, traditional coking operations base changes to the uptake damper settings on time. For example, in a forty-eight hour cycle, the uptake damper is typically set to be fully open for approximately the first twenty-four hours of the coking cycle. The dampers are then moved to a first partially restricted position prior to thirty-two hours into the coking cycle. Prior to forty hours into the coking cycle, the dampers are moved to a second, further restricted position. At the end of the forty-eight hour coking cycle, the uptake dampers are substantially closed. This manner of managing the uptake dampers can prove to be inflexible. For example, larger charges, exceeding forty-seven tons, can release too much VM into the oven for the volume of air entering the oven through the wide open uptake damper settings. Combustion of this VM-air mixture over prolonged periods of time can cause the temperatures to rise in excess of the NTE temperatures, which can damage the oven. Accordingly, there exists a need to increase the charge weight of coke ovens without exceeding not to exceed (NTE) temperatures.
Heat generated by the coking process is typically converted into power by heat recovery steam generators (HRSGs) associated with the coke plant. Inefficient burn profile management could result in the VM gases not being burned in the oven and sent to the common tunnel. This wastes heat that could be used by the coking oven for the coking process. Improper management of the burn profile can further lower the coke production rate, as well as the quality of the coke produced by a coke plant. For example, many current methods of managing the uptake in coke ovens limits the sole flue temperature ranges that may be maintained over the coking cycle, which can adversely impact production rate and coke quality. Accordingly, there exists a need to improve the manner in which the burn profiles of the coking ovens are managed in order to optimize coke plant operation and output.